CMOS image sensor having enhanced near infrared quantum efficiency

ABSTRACT

An image sensor comprises a semiconductor material having an illuminated surface and a non-illuminated surface; a photodiode formed in the semiconductor material extending from the illuminated surface to receive an incident light through the illuminated surface, wherein the received incident light generates charges in the photodiode; a transfer gate electrically coupled to the photodiode to transfer the generated charges from the photodiode in response to a transfer signal; a floating diffusion electrically coupled to the transfer gate to receive the transferred charges from the photodiode; a near infrared (NIR) quantum efficiency (QE) enhancement structure comprising at least two NIR QE enhancement elements within a region of the photodiode, wherein the NIR QE enhancement structure is configured to modify the incident light at the illuminated surface of the semiconductor material by at least one of diffraction, deflection and reflection, to redistribute the incident light within the photodiode to improve an optical sensitivity, including near-infrared light sensitivity, of the image sensor.

TECHNICAL FIELD

This disclosure relates generally to semiconductor image sensors, and inparticular but not exclusively, relates to CMOS image sensors havingenhanced near infrared (NIR) Quantum Efficiency (QE).

BACKGROUND INFORMATION

Image sensors have become ubiquitous. They are widely used in digitalstill cameras, cellular phones, security cameras, as well as, medical,automobile, and other applications. The technology used to manufactureimage sensors has continued to advance at a great pace. For example, thedemands of higher resolution and lower power consumption have encouragedthe further miniaturization and integration of these devices.

Detection of near infrared (NIR) light is useful in automotive and nightvision applications. However, conventional image sensor devices maypoorly absorb NIR light due to the band structure of semiconductormaterials used in modern microelectronic devices. Even if conventionalimage sensors can absorb NIR light, the semiconductor may need to besufficiently thick. Additional semiconductor thickness may complicateother fabrication steps and/or reduce performance.

Furthermore, many materials conductive to absorb NIR light are veryexpensive (either inherently or by virtue of fabrication techniquesneeded to process the materials), toxic, and/or have lower sensitivityto the visible spectrum. Accordingly, many elements/compounds capable ofdetecting NIR light may not be ideal choices for integration into modernelectronic devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive examples of the invention are describedwith reference to the following figures, wherein like reference numeralsrefer to like parts throughout the various views unless otherwisespecified.

FIG. 1A is a top-down view and FIG. 1B is a cross-sectional view of FIG.1A as cut along line A-A′ for an example photodiode in an image sensor,in accordance with an embodiment of the invention.

FIG. 2A is a top-down view and FIG. 2B is a cross-sectional view of FIG.2A as cut along line B-B′ for an example photodiode in an image sensor,in accordance with an embodiment of the invention.

FIG. 3A is a top-down view and FIG. 3B is a cross-sectional view of FIG.3A as cut along line C-C′ for an example photodiode in an image sensor,in accordance with an embodiment of the invention.

FIG. 4A is a top-down view and FIG. 4B is a cross-sectional view of FIG.4A as cut along line D-D′ for an example photodiode in an image sensor,in accordance with an embodiment of the invention.

FIG. 5A is a top-down view and FIG. 5B is a cross-sectional view of FIG.5A as cut along line E-E′ for an example photodiode in an image sensor,in accordance with an embodiment of the invention.

FIG. 6A is a top-down view and FIG. 6B is a cross-sectional view of FIG.6A as cut along line F-F′ for an example photodiode in an image sensor,in accordance with an embodiment of the invention.

FIG. 7A is a top-down view and FIG. 7B is a cross-sectional view of FIG.7A as cut along line G-G′ for an example front side illuminated imagingsensor, in accordance with an embodiment of the invention.

FIG. 8A is a top-down view and FIG. 8B is a cross-sectional view of FIG.8A as cut along line H-H′ for an example backside illuminated imagingsensor, in accordance with an embodiment of the invention.

FIG. 9A demonstrates light path through an example backside illuminatedimage sensor without NIR QE enhancement structures, FIG. 9B demonstratesthe simulated light density distribution in the backside illuminatedimage sensor of FIG. 9A, in accordance with an embodiment of theinvention.

FIG. 10A demonstrates light path through an example backside illuminatedimage sensor with a plurality of NIR QE enhancement structures, FIG. 10Bdemonstrates the simulated light density distribution in the backsideilluminated image sensor of FIG. 10A, in accordance with an embodimentof the invention.

FIG. 11 is the simulated QE vs. wavelength of incident light for anexample backside illuminated image sensor between the one with and theone without a plurality of NIR QE enhancement structures, in accordancewith an embodiment of the invention.

FIG. 12 is a block diagram schematically illustrating one example of animaging system, in accordance with an embodiment of the disclosure.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings. Skilled artisans willappreciate that elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale. For example,the dimensions of some of the elements in the figures may be exaggeratedrelative to other elements to help to improve understanding of variousembodiments of the present invention. Also, common but well-understoodelements that are useful or necessary in a commercially feasibleembodiment are often not depicted in order to facilitate a lessobstructed view of these various embodiments of the present invention.

DETAILED DESCRIPTION

Examples of an apparatus for an image sensor with enhanced NIR QE aredescribed herein. In the following description, numerous specificdetails are set forth to provide a thorough understanding of theexamples. However, one skilled in the relevant art will recognize thatthe techniques described herein can be practiced without one or more ofthe specific details, or with other methods, components, materials, etc.In other instances, well-known structures, materials, or operations arenot shown or described in details in order to avoid obscuring certainaspects.

Reference throughout this specification to “one example” or “oneembodiment” means that a particular feature, structure, orcharacteristic described in connection with the example is included inat least one example of the present invention. Thus, the appearances ofthe phrases “in one example” or “in one embodiment” in various placesthroughout this specification are not necessarily all referring to thesame example. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreexamples.

Throughout this specification, several terms of art are used. Theseterms are to take on their ordinary meaning in the art from which theycome, unless specifically defined herein or the context of their usewould clearly suggest otherwise. It should be noted that element namesand symbols may be used interchangeably through this document (e.g., Sivs. silicon); however, both have identical meaning.

FIG. 12 is a block diagram schematically illustrating one example of animaging system, in accordance with an embodiment of the disclosure.Imaging system 1200 includes pixel array 1205, control circuitry 1221,readout circuitry 1211, and function logic 1215. In one example, pixelarray 1205 is a two-dimensional (2D) array of photodiodes, or imagesensor pixels (e.g., pixels P1, P2 . . . , Pn). As illustrated,photodiodes are arranged into rows (e.g., rows R1 to Ry) and columns(e.g., column C1 to Cx) to acquire image data of a person, place,object, etc., which can then be used to render a 2D image of the person,place, object, etc. However, in other examples, it is appreciated thatthe photodiodes do not have to be arranged into rows and columns and maytake other configurations.

In one example, after the image sensor photodiode/pixel in pixel array1205 has acquired its image data or image charge, the image data isreadout by readout circuitry 1211 and then transferred to functionallogic 1215. In various examples, readout circuitry 1211 may includeamplification circuitry, analog-to-digital (ADC) conversion circuitry,or otherwise. Function logic 1215 may simply store the image data oreven manipulate the image data by applying post image effects (e.g.,crop, rotate, remove red eye, adjust brightness, adjust contrast, orotherwise). In one example, readout circuitry 1211 may read out a row ofimage data at a time along readout column lines (illustrated) or mayreadout the image data using a variety of other techniques (notillustrated), such as a serial readout or a full parallel readout of allpixels simultaneously.

In one example, control circuitry 1221 is coupled to pixel array 1205 tocontrol operation of the plurality of photodiodes in pixel array 1205.For example, control circuitry 1221 may generate a shutter signal forcontrolling image acquisition. In one example, the shutter signal is aglobal shutter signal for simultaneously enabling all pixels withinpixel array 1205 to simultaneously capture their respective image dataduring a single acquisition window. In another example, the shuttersignal is a rolling shutter signal such that each row, column, or groupof pixels is sequentially enabled during consecutive acquisitionwindows. In another example, image acquisition is synchronized withlighting effects such as a flash.

In one example, imaging system 1200 may be included in a digital camera,cell phone, laptop computer, automobile or the like. Additionally,imaging system 1200 may be coupled to other pieces of hardware such as aprocessor (general purpose or otherwise), memory elements, output (USBport, wireless transmitter, HDMI port, etc.), lighting/flash, electricalinput (keyboard, touch display, track pad, mouse, microphone, etc.),and/or display. Other pieces of hardware may deliver instructions toimaging system 1200, extract image data from imaging system 1200, ormanipulate image data supplied by imaging system 1200.

In one example, FIG. 7A is a top-down illustration of an example frontside illuminated image sensor 700 in the array pixel 1205 of FIG. 12, inaccordance with an embodiment of the invention. FIG. 7B is across-sectional illustration of FIG. 7A as cut along line G-G′. Thefront side illuminated image sensor 700 comprises a semiconductormaterial 711 as a substrate. In one example, the semiconductor material711 is P type doped Si substrate. Photodiode 702 is disposed in thesemiconductor material 711 to receive image light through front sidesurface 706 as an illuminated surface of the semiconductor material 711.In one example, dopants are implanted into the semiconductor material711 to form the photodiode 702. A transfer gate 703 is electricallycoupled to the photodiode 702 to transfer image charge from thephotodiode 702 in response to a transfer signal. In one example, thetransfer gate 703 includes a poly gate and a dielectric thin filmbetween the poly gate and the semiconductor material 711. A floatingdiffusion 704 is electrically coupled to the transfer gate 703 toreceive the image charge from the photodiode 702. In one example, inorder to reduce the dark current caused by the hot electrons, a frontside P+ doped layer 707 is disposed on the front side surface 706. Thefront side P+ doped layer 707 may be formed with P type doping by ionimplantation or plasma doping process. In the depicted example in FIG.7A, a reset transistor RESET is coupled to the floating diffusion 704 toreset image charge in the floating diffusion 704. Although not depictedin FIG. 7A, an amplifier transistor may also be coupled to the floatingdiffusion 704 to amplify the image charge in the floating diffusion 704.

In one example, FIG. 8A is a top-down illustration of an example backside illuminated image sensor 800 in the array pixel 1205 of FIG. 12, inaccordance with an embodiment of the invention. FIG. 8B is across-sectional illustration of FIG. 8A as cut along line H-H′. The backside illuminated image sensor 800 comprises a semiconductor material811. In one example, the semiconductor material 811 is a P type doped Silayer. Photodiode 802 is disposed in the semiconductor material 811 toreceive image light through back side surface 805 as an illuminatedsurface of the semiconductor material 811. In one example, dopants areimplanted into the semiconductor material 811 to form the photodiode802. A transfer gate 803 is electrically coupled to the photodiode 802to extract image charge from the photodiode 802 in response to atransfer signal. In one example, the transfer gate 803 includes a polygate and a dielectric thin film between the poly gate and thesemiconductor material 811. A floating diffusion 804 is electricallycoupled to the transfer gate 803 to receive the image charge from thephotodiode 802. In one example, in order to reduce the dark currentcaused by the hot electrons from the front side surface 806, a frontside P+ doped layer 807 is disposed on the front side surface 806. Thefront side P+ doped layer 807 may be formed with P type doping by ionimplantation or plasma doping process. In order to reduce the darkcurrent caused by the hot electrons from the back side surface 805, aback side P+ doped layer 814 is also disposed on the back side surface805. The back side P+ doped layer 814 may be formed with P type dopingby ion implantation or plasma doping process. The back side P+ dopedlayer 814 may also be formed by depositing a negative charged dielectricmaterial on the backside surface 805. In the depicted example in FIG.8A, a reset transistor RESET is coupled to the floating diffusion 804 toreset image charge in the floating diffusion 804. Although not depictedin FIG. 8A, an amplifier transistor may also be coupled to the floatingdiffusion to amplify the image charge in the floating diffusion 804.

As illustrated in both FIG. 7A-7B and FIG. 8A-8B, a plurality of nearinfrared (NIR) quantum efficiency (QE) enhancement structures aredisposed at the illuminated surface in the photodiode and configured tomodify the incident light at the illuminated surface of thesemiconductor material by at least one of diffraction, deflection andreflection, to redistribute the incident light within the photodiode toimprove an optical sensitivity, including near-infrared lightsensitivity, of the image sensor. In one example, each of the NIR QEenhancement structures comprises at least two NIR QE enhancementelements within a region of the photodiode.

In the depicted examples in FIG. 7A-7B, the NIR QE enhancement elements701 are disposed in the photodiode 702 at the front side surface 706where the incident light is received through. In the depicted examplesin FIG. 8A-8B, the NIR QE enhancement elements 801, which are the sameas 701, are disposed in the photodiodes 802 at the backside surface 805where the incident light is received through. Since 801 are at thebackside surface 805, they are not visible in the top down illustrationFIG. 8A.

As the examples illustrated in FIG. 7 and FIG. 8, the NIR QE enhancementelements 701 and 801 are arranged into rows and columns. Each of the NIRQE enhancement elements has a same shape as a trench structure (701 inFIGS. 7 and 801 in FIG. 8). In one example, the trench structure has 0.2um critical dimension and 0.4 um depth. Each of the NIR QE enhancementelements extends from the illuminated surface, through the P+ dopedlayer, and into the photodiodes in the semiconductor material.

In one example, each of the NIR QE enhancement elements comprises a coredielectric material which has a refractive index smaller than therefractive index of the semiconductor material. As one example, thesemiconductor material is silicon. However, one skilled in the art willappreciate that any group III elements (B, Al, Ga, In, Tl), group IVelements (C, Si, Ge, Sn, Pb), group V elements (N, P, As, Sb, Bi), andsuitable combinations of these elements, may be used to form thesemiconductor material, in accordance with the teachings of the presentinvention. In some examples, the core dielectric material may includeoxides/nitrides such as silicon oxide (SiO₂), hafnium oxide (HfO₂),silicon nitride (Si₃N₄), silicon oxynitirde (SiO_(x)N_(y)), tantalumoxide (Ta₂O₅), titanium oxide (TiO₂), zirconium oxide (ZrO₂), aluminumoxide (Al₂O₃), lanthanum oxide (La₂O₃), praseodymium oxide (Pr₂O₃),cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethium oxide (Pm₂O₃),samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), gadolinium oxide(Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide (Dy₂O₃), holmium oxide(Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide (Tm₂O₃), ytterbium oxide(Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide (Y₂O₃), or the like.Additionally, one skilled in the relevant art will recognize that anystoichiometric combination of the above metals/semiconductors and theiroxides/nitrides/oxynitrides may be used, as long as they have arefractive index smaller than the refractive index of the semiconductormaterial, in accordance with the teachings of the present invention.

Although not illustrated in FIG. 7 and FIG. 8, each of the NIR QEenhancement elements may also comprise a liner material disposed betweenthe photodiode and the core dielectric material. In some examples, theliner material may include at least one of a negatively charged high kdielectric material, or a doped semiconductor material. For example, atrench could be etched and boron, nitrogen, or arsenic could beimplanted into the sidewalls of the trench to form a doped semiconductormaterial as the liner material. Alternatively, a trench could be etchedand hafnium oxide could be deposited in the trench to form a negativelycharged high-k liner material before the core dielectric material isdeposited into the trench.

In other examples, each of the NIR QE enhancement elements may alsocomprise one shape of a parallelepiped, a polygon, cylinder, anellipsoid, a hemispheroid, and a hemisphere. They may also take otherconfigurations as long as they have a uniform critical dimensions andshape, and are disposed in a periodic pattern with consistent distancebetween adjacent NIR QE elements. Some of examples are illustrated inFIG. 1 to FIG. 6.

FIG. 1A-6A are top-down views and FIG. 1B-6B are cross-sectional viewsof FIG. 1A-6A as cut along lines for an example photodiode 102 in animage sensor of pixel array 1205 in FIG. 12, in accordance with anembodiment of the invention. Also depicted are isolation regions 103. Asone example, the isolation region 103 surrounds the photodiode 102 andextends through the semiconductor material from the illuminated surfaceso as to isolate the adjacent photodiodes 102 electrically andoptically. In one example, the isolation regions 103 may include deeptrench isolation structures. In order to keep the description consistentand simple, the isolation region is defined with the same number 103 andthe photodiode is defined with the same number 102 in FIG. 1 to FIG. 6.

As an illustrated example in FIGS. 1A and 3A, the NIR QE enhancementelements 101 are arranged as a circle pattern with one NIR QEenhancement element at the center and the rest of NIR QE enhancementelements along the circle. Each two adjacent NIR QE enhancement elementsalong the circle are separated with the same distance. As an illustratedexample in FIGS. 2A and 4A, the NIR QE enhancement elements 101 arearranged as a square pattern with one at the center and the rest at thefour corners of the square. Each two adjacent NIR QE enhancementelements at the corners are separated with the same distance.

In one example, each of the NIR QE enhancement structures may alsocomprise only one NIR QE enhancement element within a region of thephotodiode. As an illustrated example in FIG. 5A, the NIR QE enhancementelement 501 is formed with a frame pattern which is adjacent to theisolation region 103. As an illustrated example in FIG. 6A, the NIR QEenhancement element 601 is formed with a cross pattern which is at thecenter of the photodiode 102.

As an illustrated example in FIGS. 1B-2B and 5B-6B, each of the NIR QEenhancement elements is formed as a trench structure which has a samecritical dimension and a same depth. They extend from the illuminatedsurface into the photodiode and are filled with the core dielectricmaterial. Although not illustrated, each of the NIR QE enhancementelements may also comprise the liner material disposed between thephotodiode and the core dielectric material. Alternately, as anillustrated example in FIG. 3B-4B, each of the NIR QE enhancementelements may also be disposed at least partially on the top of theilluminated surface, and comprises the core dielectric material.

In an example, FIG. 9A demonstrates incident light path through twoadjacent buried color filter array (BCFA) backside illuminated (BSI)image sensors without NIR QE enhancement structures. The pixel size ofeach photodiode is 2.0 μm. The image sensors are built in 3 μm thick Silayer. A deep trench isolation (DTI) structure is disposed between twoadjacent photodiodes, a metal grid between two adjacent color filters,and two microlens on the top of respective color filters.

As illustrated in FIG. 9A, for the BCFA BSI image sensors without NIR QEenhancement structures, the incident light with different wavelength istransmitted into different depth in the Si layer. The incident lightwith longer wavelength may have deeper light path into the Si layer. Ifthe thickness of the Si layer is shorter than the depth of the incidentlight path, which usually happens to NIR incident light with wavelengthlonger than 800 nm, part of incident light may be transmitted throughthe Si layer without being absorbed by Si completely. As a result, QEmay be low accordingly. In one example, FIG. 9B is the simulatedincident light density distribution in the BCFA BSI image sensors ofFIG. 9A. The majority of NIR incident light is distributed along thelight path and transmitted through the photodiode. FIG. 11 demonstratesthe simulated QE of incident light with different wavelength based onthe same BCFA BSI image sensors as FIG. 9A. QE of incident light with850 nm wavelength is ˜15%, and QE with 940 nm wavelength is ˜11%.

As a comparison, FIG. 10A also demonstrates the incident light paththrough the same two adjacent BCFA BSI image sensors as FIG. 9A, butwith a plurality of NIR QE enhancement structures disposed in thephotodiodes at the backside surface. The NIR QE enhancement structuresare configured to have the same square pattern as FIG. 2A. Each of theNIR QE enhancement elements has a hemisphere shape with 0.2 μm radius,which is extended from the backside surface into the Si layer and filledwith SiO2. SiO2 has a refractive index about 1.45 while Si has arefractive index about 3.673. When the incident light is transmittedfrom SiO2 into the photodiode in the Si layer, the light path getsmodified at the backside surface by at least one of diffraction,deflection and reflection. Accordingly, the incident light getsredistributed within the photodiode as illustrated in FIG. 10B, whichcauses more incident light staying in the Si layer and being absorbed bySi. As a result, NIR light sensitivity of the image sensor is improved.FIG. 11 demonstrates the simulated QE of incident light with differentwavelength based on the same BCFA BSI image sensors as FIG. 10A. QE ofincident light with 850 nm wavelength is increased from ˜15% to ˜40%,and QE with 940 nm wavelength is increased from ˜11% to ˜34%. On theother hand, QE of red, blue and green light is not impactedsignificantly by NIR QE enhancement structures, because their light pathhas a depth shorter than the Si layer. Moreover, one skilled in the artwill also appreciate that DTI needs to be deep enough in order toprevent the optical and electrical cross talk between the two adjacentphotodiodes in FIG. 10A and FIG. 10B.

The above description of illustrated examples of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific examples of the invention are described herein forillustrative purposes, various modifications are possible within thescope of the invention, as those skilled in the relevant art willrecognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific examples disclosedin the specification. Rather, the scope of the invention is to bedetermined entirely by the following claims, which are to be construedin accordance with established doctrines of claim interpretation.

What is claimed is:
 1. An image sensor, comprising: a semiconductormaterial having an illuminated surface and a non-illuminated surface; aphotodiode formed in the semiconductor material extending from theilluminated surface to receive an incident light through the illuminatedsurface, wherein the received incident light generates charges in thephotodiode; a transfer gate electrically coupled to the photodiode totransfer the generated charges from the photodiode in response to atransfer signal; a floating diffusion electrically coupled to thetransfer gate to receive the transferred charges from the photodiode; anear infrared (NIR) quantum efficiency (QE) enhancement structurecomprising at least two NIR QE enhancement elements within aphotosensitive region of the photodiode, wherein the NIR QE enhancementstructure is configured to modify the incident light at the illuminatedsurface of the semiconductor material by at least one of diffraction,deflection and reflection, to redistribute the incident light within thephotodiode to improve an optical sensitivity, including near-infraredlight sensitivity, of the image sensor.
 2. The image sensor of claim 1,wherein each NIR QE enhancement element of the NIR QE enhancementstructure comprises a dielectric material having a refractive indexsmaller than a refractive index of the semiconductor material.
 3. Theimage sensor of claim 1, wherein the at least two NIR QE enhancementelements have a uniform size and shape, and are disposed in a periodicpattern.
 4. The image sensor of claim 1, wherein each NIR QE enhancementelement of the NIR QE enhancement structure comprises a shape of one ofa parallelepiped, a polygon, a cylinder, an ellipsoids, a hemispheroid,and a hemisphere.
 5. The image sensor of claim 1, wherein theilluminated surface of the semiconductor material is one of a front sidesurface and a back side surface of the semiconductor material.
 6. Theimage sensor of claim 1, wherein each NIR QE enhancement element of theNIR QE enhancement structure extends from the illuminated surface of thesemiconductor material in the photodiode.
 7. The image sensor of claim1, wherein each NIR QE enhancement element of the NIR QE enhancementstructure is disposed at least partially on the illuminated surface ofthe semiconductor material.
 8. The image sensor of claim 1, wherein anisolation region surrounds, at least partially, the photodiode, andisolates the photodiode electrically and optically.
 9. The image sensorof claim 1, further comprising a reset transistor electrically coupledto the floating diffusion to reset the charges received in the floatingdiffusion.
 10. The image sensor of claim 1, further comprising anamplifier transistor electrically coupled to the floating diffusion toamplify the charges received in the floating diffusion.
 11. An imagingsystem, comprising: a semiconductor material having an illuminatedsurface and a non-illuminated surface; a plurality of photodiodes formedin the semiconductor material extending from the illuminated surface toreceive an incident light through the illuminated surface, wherein thereceived incident light generates charges in the photodiodes; aplurality of isolation structures, wherein each of the plurality ofisolation structures is disposed between two adjacent photodiodes of theplurality of photodiodes; a plurality of transfer gates electricallycoupled to the plurality of photodiodes to transfer the generatedcharges from the plurality of photodiodes to one or more floatingdiffusions; A plurality of near infrared (NIR) quantum efficiency (QE)enhancement structures, wherein each of NIR QE enhancement structurescomprises at least two NIR QE enhancement elements within the aphotosensitive region of individual photodiode of the plurality ofphotodiodes, wherein the NIR QE enhancement structures are configured tomodify incident light at the illuminated surface of the semiconductormaterial by at least one of diffraction, deflection and reflection, toredistribute the incident light within the photodiode to improve anoptical sensitivity, including near infrared light sensitivity, of theimage system.
 12. The imaging system of claim 11, further comprising aplurality of reset transistors, wherein each of the plurality of resettransistors electrically coupled to the one or more floating diffusionsto reset the charges received in the one or more floating diffusions.13. The imaging system of claim 11, further comprising a plurality ofamplifier transistors, wherein each of the plurality of amplifiertransistors electrically coupled to the one or more floating diffusionsto amplify the charges received in the one or more floating diffusions.14. The imaging system of claim 11, further comprising a controlcircuitry and a readout circuitry, wherein the control circuitrycontrols operation of the plurality of photodiodes, and the readoutcircuitry reads out image data from the plurality of photodiodes. 15.The imaging system of claim 11, wherein each NIR QE enhancement elementof the NIR QE enhancement structures comprises a dielectric materialhaving a refractive index smaller than a refractive index of thesemiconductor material.
 16. The imaging system of claim 11, wherein atleast two NIR QE enhancement elements of the NIR QE enhancementstructures have a uniform size and shape, and are disposed in a periodicpattern.
 17. The imaging system of claim 11, wherein each NIR QEenhancement element of the NIR QE enhancement structures comprises ashape of one of a parallelepiped, a polygon, a cylinder, an ellipsoids,a hemispheroid, and a hemisphere.
 18. The imaging system of claim 11,wherein each NIR QE enhancement element of the NIR QE enhancementstructures extends from the illuminated surface of the semiconductormaterial in the photodiode.
 19. The imaging system of claim 11, whereineach NIR QE enhancement element of the NIR QE enhancement structures isdisposed at least partially on the illuminated surface of thesemiconductor material.
 20. The imaging system of claim 11, wherein theilluminated surface of the semiconductor material is one of a front sidesurface and a back side surface of the semiconductor material.